A tumor is an abnormal growth of body tissue and can be cancerous (malignant) or noncancerous (benign). Tumors, particularly cancerous tumors, are a serious threat to human well-being and their detection in early stage is critical in order to obtain effective treatment or cure. However, it is a huge challenge for conventional tumor detection methods to detect cancer earlier than symptomatically, or detect cancer at earlier stages of tumor metastasis. For example, conventional methods fail to identify about 40% of cancer patients who are in need of more or enhanced therapies. It is also important to detect any early signs of spread in cancer following cancer treatments to assess effectiveness of the treatment, as well as if and what follow-up treatment is needed. Conventional cancer detection techniques such as x-ray imaging and nuclear magnetic resonance (NMR) imaging fail to provide reliable information to the above critical applications.
Recent research and clinical studies have shown that cancer invasion to a human body may occur very early in tumor development. Early detection and early systemic therapies will result in a declining death rate from cancer. Metastasis, initiated by tumor cells transported through the circulation from the primary tumor to vital distant organs, is known to be the leading cause of cancer related deaths. The early spread of tumor cells to lymph nodes or bone marrow in peripheral blood is referred to as circulating tumor cells (CTCs or CTC). CTCs may still exist in a patient' peripheral blood even after the removal of the primary tumor.
CTCs are essential for establishing metastasis, and detection of CTCs is an important tool to assess the aggressiveness of a given tumor and its potential of subsequent growth at distant organs. Specific and sensitive detection of CTCs can be used to identify the overall cancer development or metastasis status, survival possibility, and assessment of the therapeutic response.
With more and more research on CTCs in recent years, its importance to cancer progression gets highly respected. However, CTCs exist in blood only on the order of 1 per billion to 10 billion. Present technique to separate and identify CTCs, on one hand, is quite labor intensive and expensive, and on the other hand lack accuracy and reliability. The procedure includes density gradient separation, immunomagnetic separation and density gradient immunomagnetic separation, and more hard work in dealing with the identification of the large volume filtered cells by human.
There is a pressing need to find solutions that can bring enhanced sensitivity, specificity, efficiency, convenience, and speed in early-stage CTC detection at reduced costs.